The invention relates to the treatment of tobacco in general, and more particularly to improvements in methods of and in apparatus for manipulating packages of compacted or condensed tobacco leaf laminae and/or tobacco ribs. Still more particularly, the invention relates to improvements in methods of and in apparatus for manipulating packages of compacted tobacco particles (consisting of tobacco leaf laminae and/or tobacco ribs) wherein the particles of packages are dielectrically heated by subjecting them to the action of microwaves and/or to the action of one or more electric high frequency fields.
Harvested tobacco leaves are normally subjected to a pronounced drying action so that their moisture content is reduced to approximately 8-11 percent. The thus dried tobacco is thereupon condensed into cylindrical, block-shaped or otherwise configurated packages (hereinafter called bales for short). The particles which form the bales can consist exclusively of tobacco leaf laminae (i.e., stripped tobacco leaves (also called strips) which are devoid of ribs), exclusively of tobacco ribs, or of a mixture of laminae and ribs. If the stripping of tobacco leaves takes place prior to baling, the ribs are or can be stored separately to be cut and admixed to shredded laminae in a cigarette maker or the like. An advantage of bales of compacted laminae and/or ribs is that they can be stored for extensive periods of time and occupy little room in storage and during transport.
When the particles of the bales are to be converted into fillers of cigarette rods or other tobacco-containing rods in accordance with heretofore known procedures, the bales must be broken up, i.e., the coherent particles (be it ribs and/or laminae) must be singularized in a complex and time consuming manner. The reason is that the relatively dry and hence brittle particles strongly adhere to each other so that the separating operation must be carried out with great care in order to avoid excessive comminution of the particles prior to actual cutting (e.g., shredding). It is customary to introduce a bale into a vacuum chamber and to drive into the bale one or more hollow mandrels which serve to admit steam. The thus admitted steam tends to escape into the chamber because its pressure exceeds the pressure in the chamber. This results in heating and moisturizing of the particles, i.e., the particles become or are supposed to become supple and to be readily separable from each other. Reference may be had, for example, to U.S. Pat. No. 3,372,703. A drawback of the patented procedure is that the energy requirements of the bale breaking or loosening apparatus are very high and that such apparatus are complex, bulky and expensive. As a rule, the apparatus will raise the moisture content of particles to approximately 12-14 percent which is considered an acceptable value for enhancing the suppleness of the particles and for facilitating their separation without undue breakage. Such preliminary moisturizing to between 12 and 14 percent is followed by additional moisturizing in order to raise the moisture content to between 18 and 23 percent. This is considered by experts to be an optimum moisture content of tobacco particles which consist of tobacco leaf laminae and are about to be shredded. The moisture content of tobacco ribs which are about to be cut is raised to as high as 30 percent. A modern tobacco shredder operates with two convergent chains which subject the moisturized particles to a pronounced compressing action to form a so-called cake which is fed through a mouthpiece and into the range of a set of orbiting knives serving to convert the leader of the cake into shreds. The shreds are thereupon dried in order to reduce their moisture content to a value (e.g., between 12.5 and 13.5 percent) which is satisfactory or best suited for gathering of shreds into a stream in a cigarette rod making machine.
The above outlined steps of a conventional method of breaking up bales and of converting their particles into shreds which are ready for the making of tobacco fillers involve heating and moisturizing, additional moisturizing, pronounced compacting in the shredder and subsequent drying. This consumes much energy and contributes significantly to the cost of the ultimate products.
U.S. Pat. No. 4,799,501 to Liebe et al. discloses a modified method and apparatus wherein the vacuum chamber is replaced with a microwave oven. The oven heats the particles of bales and weakens the bonds between neighboring particles. The loosened particles are wetted in order to raise their moisture content to a value which is considered to be best suited for conversion into a cake between the convergent chains of a shredder. Shredded particles of tobacco are thereupon dried down to the moisture content which is necessary for introduction into a cigarette rod making machine. Thus, though the method and apparatus of Liebe et al. dispense with moisturizing of particles which are condensed into bales, it is still necessary to moisturize the loosened particles prior to shredding and to thereupon dry the shredded particles preparatory to further processing, e.g., into the fillers of cigarette rods. Such moisturizing and drying steps involve the expenditure of considerable amounts of energy.
Published British patent application No. 2 187 632 discloses a method and an apparatus wherein bales of condensed and relatively dry tobacco particles are heated by subjecting them to the action of microwaves. The thus treated bales are fed into a cutting or comminuting machine prior to cooling of the particles back to starting temperature. The accumulations or packages which are being fed into the cutting machine must have a predetermined width and height; therefore, it is often necessary to break up the bales into fragments for the purpose of admitting the fragments into the cutting machine. The breaking up of bales into smaller portions or fragments which are ready for admission into the cutting machine is costly and takes up much time. In addition, remnants of bales which do not have the required width and height must be shredded or otherwise comminuted in separate machines.